Large multi-domain baseplate wedge protein (gp7; 1032 residues) of bacteriophage T4 that forms the structural backbone of each of the six baseplate wedges, bridging the peripheral tail-fiber sockets to the inner baseplate ring. During tail morphogenesis, a single gp7 monomer initiates wedge assembly by binding a gp10 homotrimer—forming an inter-subunit disulfide bond with one gp10 protomer—and subsequently recruits a gp8 homodimer and a gp6 homodimer to assemble the (gp6)2-gp7 heterotrimeric core. As part of the gp25-(gp6)2-gp7 module, gp7 transmits the receptor-binding conformational signal from the peripheral tail-fiber network to the inner baseplate during the dome-to-star transition to trigger tail sheath contraction.
| GO Term | Evidence | Action | Reason |
|---|---|---|---|
| GO:0098003 viral tail assembly | IEA GO_REF:0000043 | ACCEPT | Summary: Automated keyword annotation correctly captures the essential scaffolding role of gp7 in initiating and organizing baseplate wedge assembly. Reason: gp7 initiates baseplate wedge morphogenesis by binding the gp10 trimer and sequentially scaffolding gp8, gp6, gp53, and gp25 into mature wedges. Supporting Evidence: file:BPT4/7/7-uniprot.txt Intermediate/inner baseplate protein (PubMed:15315755, PubMed:27193680). The gp25-(gp6)2-gp7 module is involved in sheath contraction (PubMed:27193680). Involved in the tail assembly (PubMed:21129200). file:BPT4/7/7-deep-research-falcon.md gp7 is a major **structural “backbone” protein** of a baseplate wedge. It (i) scaffolds/links other wedge proteins during assembly and (ii) participates in transmitting the host-binding signal from the tail fiber/receptor-binding network to the inner baseplate, enabling the conformational transition that triggers sheath contraction. |
| GO:0098015 virus tail | IEA GO_REF:0000043 | MODIFY | Summary: Correct parent cellular component term that should be refined to the baseplate subcompartment. Reason: Within the virion tail, gp7 is an integral component of the baseplate wedges (GO:0098025). Proposed replacements: virus tail, baseplate Supporting Evidence: file:BPT4/7/7-uniprot.txt Intermediate/inner baseplate protein (PubMed:15315755, PubMed:27193680). The gp25-(gp6)2-gp7 module is involved in sheath contraction (PubMed:27193680). Involved in the tail assembly (PubMed:21129200). file:BPT4/7/7-deep-research-falcon.md gp7 is a major **structural “backbone” protein** of a baseplate wedge. It (i) scaffolds/links other wedge proteins during assembly and (ii) participates in transmitting the host-binding signal from the tail fiber/receptor-binding network to the inner baseplate, enabling the conformational transition that triggers sheath contraction. |
| GO:0098025 virus tail, baseplate | IEA GO_REF:0000120 | ACCEPT | Summary: Automated annotation accurately places gp7 in the viral tail baseplate. Reason: Six copies of gp7 (one per wedge) form the central structural backbone of the bacteriophage T4 baseplate wedges. Supporting Evidence: file:BPT4/7/7-uniprot.txt Heterotrimer with gp6; assembles as a (gp6)2-gp7 heterotrimeric molecule. The (gp6)2-gp7 heterotrimeric molecule further interacts with gp25 and gp53. file:BPT4/7/7-deep-research-falcon.md gp7 is a major **structural “backbone” protein** of a baseplate wedge. It (i) scaffolds/links other wedge proteins during assembly and (ii) participates in transmitting the host-binding signal from the tail fiber/receptor-binding network to the inner baseplate, enabling the conformational transition that triggers sheath contraction. |
| GO:0098025 virus tail, baseplate | IDA PMID:27193680 Structure of the T4 baseplate and its function in triggering... | ACCEPT | Summary: Near-atomic cryo-EM structures of the T4 baseplate resolve full-length gp7 spanning the intermediate and inner baseplate wedge regions. Reason: Taylor et al. (2016) resolved the multi-domain architecture of gp7 within the 6-MDa baseplate in both pre- and post-attachment states, including its triple-helical bundle with (gp6)2 and its disulfide linkage to gp10. Supporting Evidence: PMID:27193680 Here we present the atomic structure of the approximately 6-megadalton bacteriophage T4 baseplate in its pre- and post-host attachment states and explain the events that lead to sheath contraction in atomic detail. file:BPT4/7/7-uniprot.txt Heteromultimer with gp10; a gp10 molecule is disulfide-linked to gp7 and the other two remaining gp10 molecules form a disulfide bond. file:BPT4/7/7-deep-research-falcon.md gp7 is reported to be **covalently linked to gp10** via the only known inter-protein covalent bond in T4, and this linkage is implicated in maintaining the baseplate structure through the conformational switch. |
| GO:0039660 structural constituent of virion | IDA PMID:27193680 Structure of the T4 baseplate and its function in triggering... | NEW | Summary: Six copies of gp7 form the multi-domain structural backbone of the six baseplate wedges in the bacteriophage T4 virion tail. Reason: Near-atomic cryo-EM structures of the T4 baseplate (PMID:27193680) establish that gp7 is the largest structural scaffold of each baseplate wedge, bridging the peripheral tail-fiber sockets to the inner (gp6)2-gp7-gp25 ring. Supporting Evidence: PMID:27193680 Here we present the atomic structure of the approximately 6-megadalton bacteriophage T4 baseplate in its pre- and post-host attachment states and explain the events that lead to sheath contraction in atomic detail. file:BPT4/7/7-deep-research-falcon.md gp7 is a major **structural “backbone” protein** of a baseplate wedge. It (i) scaffolds/links other wedge proteins during assembly and (ii) participates in transmitting the host-binding signal from the tail fiber/receptor-binding network to the inner baseplate, enabling the conformational transition that triggers sheath contraction. |
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Download this section (compressed HTML)Q: How does the inter-protein disulfide bond between gp7 and one protomer of the gp10 homotrimer form within the reducing cytoplasm of Escherichia coli during late T4 morphogenesis?
Suggested experts: Petr G. Leiman, Fumio Arisaka
Q: Is the covalent disulfide linkage between gp7 and gp10 strictly required to prevent peripheral wedge dissociation under the mechanical tension of the dome-to-star transition, or can non-covalent contacts suffice for single-cycle infectivity?
Suggested experts: Petr G. Leiman, Nicholas M. I. Taylor
Experiment: Mutate the cysteine residue in gp7 that forms the inter-protein disulfide bond with gp10 to serine or alanine, and evaluate wedge assembly, virion thermal/mechanical stability, and plating efficiency.
Hypothesis: Loss of the gp7-gp10 disulfide bond will permit non-covalent wedge assembly in vitro but cause premature unpinning or detachment of the gp10-gp11-gp12 peripheral pin module during the dome-to-star transition, reducing infection efficiency.
Type: Site-directed mutagenesis, non-reducing SDS-PAGE, and phage infectivity assays
Experiment: Use single-molecule Forster resonance energy transfer (smFRET) on fluorescently labeled gp7 in reconstituted gp10-gp7 versus gp10-gp7-gp8 complexes to measure conformational dynamics of the gp7 inter-domain linker.
Hypothesis: Binding of the gp10 trimer stretches the flexible gp7 linker into a fluctuating open state that is locked into a rigid conformation upon gp8 dimer binding, exposing the gp6-binding helix.
Type: Single-molecule FRET (smFRET) of sequential wedge assembly intermediates
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